Thin film for vertical form fill and seal packaging of flowable materials

ABSTRACT

A multi-layer film for vertical form, film and seal systems for liquid, powder, granules and/or other flowables packaging, said multi-layer comprising: an inner layer made of polyethylene, a blend of polyethylenes or ethylene copolymers; a core, comprising one or more than one layer, made from a blend of polypropylene, linear low density polyethylene, a polymer compatibilizer or tie-layer resin, and/or low density polyethylene, said core being applied against the inner layer; and an outer layer (same or different from the inner layer or the core layer) is made of a polyethylene or a blend of polyethylenes with or without ethylene copolymers, said outer layer being applied against the core and opposite the inner layer; said multi-layer film having an overall thickness of lower or equal to 2.5 mil and at least one of the properties listed hereinafter: a stiffness (as measured by 1% secant modulus in the film machine direction) varying from 3500 psi to 150000 psi; a tensile strength at yield of from 1700 psi to 3300 psi; (measured in film machine direction) and a tensile strength at break of from 4300 to 7400 psi (measured in film machine direction). A method of forming, sealing and filling a pouch with said film, a pouch formed with said film and use of said film to form a pouch.

This is a continuation-in-part application of U.S. patent applicationSer. No. 11/412,980 filed Apr. 28, 2006, the content of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to an improved thin film for vertical form, filland seal (VFFS) systems for packaging any kind of flowable materials(preferably liquids such as milk).

DESCRIPTION OF THE PRIOR ART

Film for vertical form, fill and seal (VFFS) systems for liquidpackaging must travel well through a vertical form, fill and sealmachine (i.e. have good machinability) and have the ability to be easilysealed. In addition, film for milk pouches are required to besufficiently stiff so that they can stand upright in a jug. Thisfacilitates the pouring of the milk from the plastic pouch. There aresignificant advantages of being able to prepare thin films which may beused in high speed form, fill and seal (FFS) systems. One of theseadvantages is the increased number of pouches—i.e. the yield—from eachpound of film. However, the stiffness of the film should not becompromised during the “down-gauging” of the material. Indeed it has tobe enhanced to ensure that the pouch can remain standing in the jug.

Recently it has been described in U.S. Pat. No. 6,237,308B1 (Quintin etal.) assigned to Glopak Inc., a multi-layer film structure withpolyethylene sealant layers and a core made up of a blend polypropylene(PP) and low density polyethylene (LDPE) to improve the strength of theheat sealed pouches prepared by VFFS machines. The core may also containlinear low density polyethylene (LLDPE) in the blend of LDPE and PP.

Theoretically, this film structure reduces the thinning of the plasticin the area of the seal because at the pressure and temperature usedduring the sealing of the pouch, the polypropylene (PP) is less fluidand mobile compared to the sealant layer polymer blend. There is atendency for the film at the seal to stretch and thin out because of thecombined effect of the temperature, pressure between the sealing jaws,and weight of the contents of the pouch pulling on the film duringsealing.

The maximum VFFS filling speed attainable with the use of this film islimited unless the amount of polypropylene (PP) in the core is low. Athigh levels of polypropylene the quality of the seals suffer because ofincompatibility between the polypropylene and the low densitypolyethylene (LDPE) in the core. This incompatibility causes theprecipitation of grains of polypropylene (PP) or polypropylene (PP)together with polyethylene (PE) in separate phases and results in thecreation of hard inclusions in the area of the seal. The problem isexacerbated at higher levels of polypropylene (PP). Also, if the sealedpouches are kept in the cold, as would be expected for a refrigeratedproduct, the number and size of the hard inclusions/nodules mayincrease.

SUMMARY OF THE INVENTION

The present invention relates to a technical advance to the art whichallow the creation of a multi-layer film without the problems of theinclusion of nodules in the seal area even if the proportion of PP inthe film core is high. A purely illustrative and non limiting example ofa high PP proportion may be upwards of 40% w/w in the core of amultilayer film. This film also seals more rapidly because it showsenhanced heat transfer characteristics.

The Applicant has noted that the higher is the proportion of PP in thefilm, higher is the required temperature of the sealing jaws. Also, theApplicant has noted that if a polymer compatibilizer (such as forexample EMAC (ethylene methacrylate copolymer) or any other polymercompatibilizers) is present in the blend of polymers used in the core,when the amount of PP increases, the relative increase of the requiredsealing temperature to obtain the same quality seal is less (whencompared to a film having no polymer compatibilizer of the low meltingmulti-functional variety).

Apparently, without being formally bound to the followinginterpretation, this may be owed to the fact that the coefficient ofthermal conductivity of PP is lower than for LLDPE. Therefore the higheris the proportion of PP in the core, lower is the rate of heat transferacross the film during sealing. However, if a polymer compatibilizer(e.g. EMAC or other polymer compatibilizers) is introduced in the core,the melt temperature of the core is lowered. The Applicant has notedthat when the core is partially molten during sealing, a more rapidtransfer of heat across the film is obtained.

More particularly, according to a first preferred embodiment, thepresent invention relates to a multi-layer film for vertical form, filland seal systems for liquid, powder, granules and/or other flowablespackaging, said multi-layer comprising:

-   -   an inner layer made of polyethylene, or a blend of one or        several polyethylenes and/or one or several ethylene copolymers        (preferably a blend of one or several polyethylenes with or        without one or several ethylene copolymers);    -   a core, comprising one or more than one layer, made from a blend        of:        -   polypropylene;        -   linear low density polyethylene;        -   a polymer compatibilizer or tie-layer resin; and/or        -   optionally low density polyethylene;    -   said core being applied against the inner layer; and    -   an outer layer (same or different from the inner layer or the        core layer) made of a polyethylene or a blend of polyethylenes        with or without ethylene copolymers, said outer layer being        applied against the core and opposite the inner layer;

said multi-layer film having an overall thickness lower or equal to 2.5mil, preferably an overall thickness varying from 1.75 mil to 2.5 mil.More particularly said multi-layer film may further have at least one ofthe properties listed hereinafter:

-   -   a stiffness (as measured by 1% secant modulus (ASTM D 882) in        film machine direction) varying from 3,500 psi to 150000 psi;    -   a tensile strength at yield of from 1700 to 3300 psi (ASTM        D882), measured in film machine direction); and    -   a tensile strength at break of from 4300 psi to 7400 psi        (measured in film machine direction).

The aforesaid multilayer film may optionally further comprise of atleast one additional layer adjacent the inner layer or the outer layer.Additional layer(s) may be identical or different from the onespreviously described for the inner and outer layers and the core layers.Optionally a polymer compatibilizer may be used, said polymercompatibilizer being as previously mentioned for the above mentionedcore layer. Preferably, said additional layer(s) are within thedefinitions already given hereinbefore for the inner and outer layersand for the core. Also, the eventual polymer compatibilizer ispreferably within the definition of those defined herein below aspolymer compatibilizers.

Depending on the required film strength and thickness or the rapidnessof sealing required the relative thickness of the film layers(outer:core: inner) may vary within large limits. Preferably, aforesaidratio of the relative thickness of the film layers can be 10:80:10 up30:40:30. Films with thicker skins have the ability to seal morequickly, while films with a relatively thick core and with a highproportion of PP in the core are stronger. It is more preferablyconvenient to have the following relative proportions of outer skinlayer to core layer to inner skin layer 25:50:25.

It is to be noted that a measure made according to 1 or 2 percent secantmodulus is well known to skilled workmen as a standard engineeringmeasure concerning physical properties characterization of a film. Inthis regard, a man skilled in the art may refer to ASTM D882. Also, aman skilled in the art should not require any further clarification.Such information is normally included the technical data sheets suppliedby resin manufacturers for their film resins. It is similar to theYoung's modulus except it recognizes the fact that the initial portionof the stress vs strain curve for plastic materials is not linear and soit does the measurement at a one (1) or two (2) percent offset.

Furthermore, according to a second preferred embodiment, the inventionrelates to a method of forming, sealing and filling a pouch with aliquid, powder, granules and/or other flowables at high speed on avertical form, fill and seal system, said method comprising the stepsof:

-   -   i) providing, in roll form, a multi-layer film as defined        hereinabove,    -   ii) drawing said film, by drawing means, over a pouch former to        form a plastic film tube having an overlapped vertical film        edge,    -   iii) sealing said overlapped vertical edge with a vertical        sealer to form a vertical seal,    -   iv) effecting a horizontal seal across said plastic film tube        with a horizontal sealing jaw and at a predetermined location        below said vertical sealer, and simultaneously severing said        tube to form a top horizontal seal for a filled pouch and a        bottom horizontal seal for a pouch being filled, said horizontal        and vertical seals, and    -   v) continuously feeding a liquid, powder, granules and/or other        flowables within said plastic film tube below said vertical        sealing jaw and above said transverse sealing jaw,        the resulting pouch having walls provided with a thickness lower        or equal to 2.5 mil, preferably varying from 1.75 mil to 2.5        mil. More preferably, said thickness may vary from 2.0 to 2.25        mil.

Furthermore, according to a third preferred embodiment, the inventionrelates to a pouch obtained from a multi-layer film as definedhereinabove and by processing on a vertical, forming, sealing andfilling system, said pouch having walls provided with a thicknesscorresponding to the thickness of said film which is lower or equal to2.5 mil, preferably said thickness varying from 1.75 to 2.5 mil.

Furthermore, according to a fourth preferred embodiment, the inventionrelates to a use of a multi-layers film as defined hereinabove forpreparing a pouch having walls provided with a thickness correspondingto the thickness of said film which is lower or equal to 2.5 mil,preferably said thickness varying from 1.75 to 2.5 mil on a high speedvertical form, film and seal systems. Preferably, said wall may have athickness varying from 1.75 to 2.5 mil, especially for the packaging of0.8 to 1.7 kg of liquid, powder, granules and/or other flowables.

Advantageously, according to a fifth particularly preferred embodimentof the invention, the multi-layer film according to the invention may beprepared by any appropriate process well known to skilled workman.

Advantageously, it is to be noted that thinner films (i.e. thickness<1.75 mil) maybe used to package smaller quantities of liquids, powder,granules and/or other flowables. According to a more particularlypreferred aspect of the invention, said multi-layer film may furtherhave at least a stiffness (as measured by 1% secant modulus in filmmachine direction) varying from 3,500 psi to 150 000 psi and morepreferably from 79000 psi to 140000 psi.

Preferably, as the film thickness is reduced it may be advantageous tomodify the composition of the film core by for example increasing thepercentage of polypropylene such that the film stiffness is increased.By way of illustrative and non limiting examples, we may thenconveniently vary film stiffness with thickness such that:

-   -   1. A film with a thickness of 2.5 mil has a stiffness of at        least 480 MPa (69,618 psi);    -   2. A film with a thickness of 2.25 mil has a thickness of at        least 658 MPa (95,498 psi);    -   3. A film with a thickness of 2.00 mil has a thickness of at        least 938 MPa (135,973 psi).

The aforesaid variation in film stiffness as a function of thickness isoffered as an illustrative and non limiting example of how one may“downgauge” and still have a film that is stiff enough to be used topackage a fluid (such as for example milk) in a VFFS pouch. According tothis particularly preferred application, the stiffness and thickness ofthe multi-layer film is such that the pouch obtained could remainupright in the jug/container.

Alternatively, it may be preferably possible however to chose to makethe thicker film be stiffer than required for the particularapplication.

More particularly, the present invention relates to the fact that lowdensity polyethylene limits the performance of the film, and that a muchsuperior structure is created by lowering and preferably eliminating theLDPE in the core of multi-layer structures which contain polypropylene(PP). The superior structure is created because LDPE is not particularlycompatible with PP. The lack of compatibility contra-indicates the useof high levels of PP in the core of the film. However high levels of PPare desirable for the creation of a stiffer and stronger film.

The use of the compatibilizer reduces the tendency of the linear lowdensity polyethylene (LLDPE) and the polypropylene (PP) to form separatephases and prevent the formation of hard nodules of polymers (or polymerblends) in the seal area of the film when high levels of polypropylene(PP) are used. This also facilitates faster film sealing since at alower temperature the compatibilizer promotes the melting of the filmlayers. Also, this melting, whether in whole or in part, furthercontributes to promote the transfer of heat from the sealing elementthrough the film to the sealant layer on the inside wall of the pouch. Arapid transfer of heat through the pouch wall facilitates the melting ofthe sealant surfaces such that the necessary interpenetration of polymerchains which is required to have good seals occurs.

If high levels of polypropylene (PP) are present in the core of themulti-layer film and there is no compatibilizer, such as for example thelower melt temperature ethylene methacrylate copolymer (EMAC) the rateof heat transfer across the film structure tends to go down relative tothat which would occur if the film had a polyethylene (PE) core. This isone consequence of the fact that the coefficient of thermal conductivityof polypropylene (PP) is less than that of polyethylene under theconditions typically used during the sealing of polyolefin or relatedfilm structures in VFFS equipment. In addition to the increased rates ofheat transfer and therefore the possibility of more rapid sealing; thefilm structure has better integrity because the compatibilizer helps to“weld” the multiple layers of film together, i.e. the tendency for filmlayer de-lamination is less.

Another preferred aspect of the invention relates to the fact that theuse of the compatibilizer such as EMAC (ethylene methacrylate copolymer)make the film blend more supple and pliable. This increased supplenessis due to the fact that the functional group on the compatibilizer ismore bulky than the usual ethylene or propylene group. Thus introductionof this polymer into the resin blends causes the crystallized polymer inthe film to be more open, and indeed, somewhat less crystalline. The netresult is—all things being equal- a film that is more supple whencertain compatibilizers such as for example EMAC, is/are incorporated inthe film. This contributes to improved film machinability; since itallows it to pass over structures, such as the tube former or morespecifically the “forming shoulders” in the VFFS machine withoutbecoming permanently creased. Films with high levels of PP in PP-LLDPEor PP-LDPE blends tend to crease and “stress-whiten” when folded. Thetendency for this permanent defect to occur in folded film is markedlyless when a compatibilizer such as EMAC is included in the resin blend.Its incorporation “softens” the film without compromising unduly thestrength and stiffness of the film.

Another preferred embodiment of the invention relates to theintroduction of a clarifier either by the use of pre-clarified PP grade,or by separate addition, to create a clear film even when high levels ofPP are present in the blend. A clearer film is desirable for thepackaging of milk, liquids, and/or other flowables. The clearer filmoffers the consumer and packager an opportunity to assess productquality by eye. The clarifier improves the aesthetic appeal of the filmwithout compromising the physical properties of the film. The mechanismof clarification requires that the PP layer is nucleated to such anextent that many small PP spherulites are produced upon cooling asopposed to fewer spherulites than can grow to create larger particles ofPP or PP-PE blends.

An additional benefit of the greater degree of nucleation in thepresence of the clarifier is that it contributes to the reduction in theformation of hard nodules at the area of the film seal during VFFSoperation. Typically these hard nodules grow when the film cools in thearea of the seal. They can continue to grow during the storage of thesealed milk pouches. If the amount of compatibilizer used is sufficient,then it is not necessary to add a clarifier for the purpose ofeliminating the creation of nodules in the area of the film seal. Sooptionally—as a non-limiting example-one may choose to increase theamount of EMAC in the core to 8% (w/w percent) and not include aclarifying agent if the core has 70% w/w of polypropylene and 20% w/w ofLLDPE.

A skilled workman knows the suitable polypropylene (PP) clarifiersand/or nucleating agents which may be used. Preferably, such clarifiermay be selected from the group consisting of 4-biphenyl carboxylic acid,thymine, talc, sodium benzoate or dibenzylidene sorbitol (DBS); bis(p-methyl-dibenzylidene sorbitol) (MDBS) and related sorbitolderivatives. The amount of clarifier that may be preferably typicallyused may represent from 0.05 to 0.5% w/w of the total composition of themulti-layer film.

Particularly preferred multi-layer film structures according to theinvention have been developed with a high proportion of polypropyleneblended with linear low density polyethylene and a polymercompatibilizer in the core. These new film structures can be used athigh speed in VFFS systems because there is no precipitation ofpolyethylene (PE), polypropylene (PP) or PP-PE blends that areincompatible with the bulk polymer solid solution at the at the sealingzone. The presence of such precipitated material in the area of the sealcompromises seal quality. The new film structures provide significantimprovements over traditional film structures even when the gauge of thenew structure is less, because the higher proportion of polypropylene inthe core enhances the strength and stiffness of the film.

This development leads to a significant improvements to the art becauseit allows:

-   -   i) The down-gauging of film for the VFFS packaging of milk and        other liquids and/or flowable material, with the concomitant        improvements in film yield and reduction in scrap;    -   ii) Faster film sealing without the creation of nodules or        inclusions of material of a different phase or crystalline        structure in the sealing zone;    -   iii) The incorporation of a polymer with a higher melt        temperature, stiffness and strength in the film core; and    -   iv) The creation of a film for VFFS with a significant amount of        a stiff polymer such as PP which is nevertheless supple and        pliable enough to not become creased when folded or pulled        across forming shoulders—of the tube former—and other structures        in the VFFS machine.

These improvements to the art are of great benefit to the VFFS milk,liquid and/or other flowables packaging industry.

BRIEF DESCRIPTION OF THE DRAWINGS

Particularly preferred embodiments of the invention will be describedhereinafter with reference to the following drawings:

FIG. 1 is a schematic diagram illustrating basic component parts ofhigh-speed pouch forming, sealing and filling machine;

FIG. 2 is a schematic view of a process for the preparation of amultilayer film;

FIG. 3 is a graphic expression of the film stress at yield for selectedfilms manufactured in the manner of the invention;

FIG. 4 is a graphic expression of the film stiffness for selected filmsmanufactured in the manner of the invention;

FIG. 5 is a graphic expression of the film stress at break for selectedfilms manufactured in the manner of the invention;

FIG. 6 is a graphic expression of the film stress at break (crossdirection) for selected films manufactured in the manner of theinvention; and

FIG. 7 is a graphic expression of the break strength (machine direction)as a function of the percentage of polypropylene (PP) for selected filmsmanufactured in the manner of the invention.

DETAILED DESCRIPTION OF PARTICULARLY PREFERRED EMBODIMENTS

According to a first particularly preferred embodiment, the inventionrelates to a multi-layer film for vertical form, fill and seal systemsfor liquid, powder, granules and/or other flowables packaging, saidmulti-layer comprising:

-   -   an inner layer made of polyethylene, or a blend of one or        several polyethylenes and/or one or several ethylene copolymers        (preferably a blend of one or several polyethylenes with or        without one or several ethylene copolymers);    -   a core, comprising one or more than one layers, made from a        blend of:        -   polypropylene;        -   linear low density polyethylene;        -   a polymer compatibilizer or tie-layer resin; and/or        -   optionally low density polyethylene;    -   said core being applied against the inner layer; and    -   an outer layer (same or different from the inner layer or the        core layer) made of a polyethylene or a blend of one or several        polyethylenes and/or one or several ethylene copolymers        (preferably a blend of one or several polyethylenes with or        without one or several ethylene copolymers), said outer layer        being applied against the core and opposite the inner layer;        said multi-layer film having an overall thickness lower or equal        to 2.5 mil, preferably an overall thickness varying from 1.75 to        2.5 mil, and at least one of the properties listed hereinafter        (for a typical multi-layer film with outer layer:core layer:        inner layer with relative proportions of 25:50:25):    -   a stiffness (as measured by 1% secant modulus in the film        direction ) varying from 3500 psi to 150000 psi, more preferably        79 000 psi to 140 000 psi;    -   a tensile strength at yield of from 1700 psi to 3300 psi        (measured in film machine direction); and    -   a tensile strength at break of from 4300 psi to 7400 psi (as        measured in the film's machine direction), preferably 5000 to        6500 psi (machine direction).

Preferably, the polypropylene may be a random copolymer polypropylene orblend of homo-polymer polypropylenes and/or copolymer polypropylene. Toprepare a high impact strength version of the film the grade ofpolypropylene or blend of polypropylene(s) used will be such that theizod impact strength of the PP is greater than 9 ft.lb_(f) per inch ofnotch as per American Society for Testing and Materials (ASTM) standardD256. More preferably, a particularly suitable polypropylene may be ahigh impact copolymer blown film grade with an izod impact strength(ASTM D257, at 23° C.) of from 8 to 80 lb/f per inch of notch., and meltflow index (ASTM D1238, 2.16 kg, 230° C.) of from 0.3 to 5.5 g/10 min

Preferably, the linear low density polyethylene (LLDPE) for the corelayer preferably may have a melt index (ASTM D1238, 2.16 kg, 190° C.)from 0.4 to 2.00 g per 10 minutes and a density of approximately 0.926g/cc. An LLDPE with a higher melt index maybe used provided thetemperature at which the film is extruded is sufficiently low to ensurethat the film has the correct melt strength to allow successfulblowing—and/or casting—into film. A man skilled in the art may choose touse an LLDPE of a higher or lower density, as a means of modifying thefinal puncture resistance or tensile strength of the film. Morepreferably, a particularly suitable polyethylene may be a linear lowdensity polyethylene (LLDPE) with a melt index from 0.3 to 1.0.

Preferably, the polymer compatibilizer may be selected from the groupconsisting of ethylene methacrylate, ethylene methacrylate copolymer,ethylene butyl acrylate, ethylene vinyl acetate, ethylene propylenediamine rubber, ethylene propylene copolymer, ethylene styrenecopolymer, and ethylene thermoplastic elastomers. As one skilled in theart would realize, the higher the proportion of copolymer content in anethylene-copolymer type compatibilizer, the lower the amount ofethylene-copolymer type compatibilizer would be required. Thus by way ofillustrative and non limiting example, one may use 8% of a 20%methacrylate content EMAC or 7% of 24% methacrylate content EMAC andachieve similar degrees of compatibilization of the polymer blend in thecore of the film. More preferably, said compatibilizer may be such as,but not limited to one of ethylene methacrylate (EMA), ethylenemethacrylate copolymer (EMAC), ethylene vinyl acetate (VA), ethylenepropylene diamine rubber (EDPM), Versify® (ethylene propylenecopolymer); ethylene styrene copolymer (Index® copolymers), Engage®,Lotryl® and/or the tie-layer polymers between PP and PE. A 20%methacrylate content ethylene methacrylate copolymer (EMAC) isparticularly convenient for use in this application. A particularlypreferred compatibilizer is ethylene methacrylate copolymer with 20% ormore of methacrylate content. (Advantageously, when the polymercompatibilizer comprises ethylene methacrylate copolymer (EMAC), it mayhave from 10 to 25% of methacrylate content.)

Material that works as compatibilizers often also works as tie-layerresins. Any tie-layer polymer well known to skilled workmen asappropriate to bind PP with PE may be used. Preferably, said tie-layerpolymers may be selected from the group consisting of ethylenemethacrylate (EMA), ethylene methacrylate copolymer (EMAC), ethylenevinyl acetate (VA), ethylene propylene diamine rubber (EDPM), Versify®(ethylene propylene copolymer); ethylene styrene copolymer (Index®copolymers), Engage®, Lotryl® other functional copolymers orter-polymers, other ethylene propylene copolymers; anhydride or maleicanhydride modified linear low density polyethylene, modified ethyleneacrylate carbon monoxide ter-polymers, and ethylene ethyl acrylatecopolymer (EEA). A particularly prefered tie-layer resin is ethylenemethacrylate copolymer with 20% or more of methacrylate content.

Preferably, the low density polyethylene (LDPE) may have a densityvarying from 0.918 to 0.925 g/cc and melt index varying from 0.20 to 1.0g/10 min.

A particularly preferred polymer blend for the inner layer may becomprised of from 70 to 100% of an Ultra Low Density Ethylene/OcteneCopolymer (ULLDPE density 0.905 g/cc to 0.914 g/cc, ASTM D1238 (2.16 kg,190° C) melt index index of 0.5 to 1.2 g/10 min) or a metallocenecatalysed hexene very low density polyethylene (mVLDPE, density 0.905,to 0.914 g/cc with melt index of 0.5 to 1.2 g/10 min (ASTM D1238, 2.16kg, 190° C.). Advantageously, this lower density polyethylene may beprofitably blended with a fractional melt low density polyethylene toimprove the melt strength and assure better bubble stability duringblown film extrusion. However if the appropriate extrusion conditionsare chosen it is not necessary to add the low density polyethylene tothe formulation. The Applicant has noted that the use of the lowerdensity ULDPE or mVLLDPE causes the inner skin to have a relatively lowseal initiation temperature. The Applicant has also noted that a lowerseal initiation temperature promotes greater speed in the vertical formfill and seal (VFFS) operation , since the rate limiting step is oftenthe rate at which pouches can be made and sealed.

Preferably, without being bound to the following process of preparation,said multi-layer film may be prepared according to a process comprisinga multilayer blown film processing extruder such that two skin layersand a core with at least one layer is prepared. The skin layers may beprepared with a blend of linear low density polyethylenes with a densitysuch that the seal initiation temperature is sufficiently low to achieverapid sealing during VFFS operation. The LLDPE may preferably havedensities from 0.915 g/cc to 0.89 g/cc. The core may be a single layerof a polypropylene blended with a polypropylene polyethylenecompatibiliser. A suitable compatibiliser may be preferably ethylenemethacrylate copolymer (EMAC) with a methacrylate content of 20%, or oneor another (or combination there of) from the list of compatibilisersand/or tie-layer resins provided above. The core may also be a singlelayer of polypropylene (PP) blended with linear low density polyethylene(LLDPE) and a compatibiliser such as ethylene methacrylate copolymer(EMAC) or one or another polymer selected from the list ofcompatibilisers discussed above. Preferably the film may be preparedwith a blow up ratio (B.U.R) of at least 2. A multilayer core may alsobe produced, of layers of polypropylene or polypropylene-polyethyleneblends with a suitable compatibiliser or tie-layer polymer such as EMACor other material detailed herein.

Preferably, said multi-layer film may be used for the vertical form andseal packaging of 200 grams or more of liquid, powder, granules and/orother flowables. More preferably, a liquid is packaged such as a nonlimiting- example milk.

More particularly, the fluid packaging is liquid, (or powder, granulesand/or other flowables) packaging and the blend defining the core layercomprises in weight percent:

-   -   10% to 90% of polypropylene or a mixture of polypropylenes;    -   80% to 0% (preferably the lower limit of 0% is excluded from the        range) of a linear low density polyethylene (LLDPE) or a mixture        of linear low density polyethylenes (LLDPEs) and low density        polyethylene (LDPE); and    -   2% to 10% of at least one polymer compatibilizer.

Advantageously, an appropriate amount of clarifier may be optionallyfurther added. Preferably, such a clarifier may be of any kind wellknown to skilled workmen. More preferably, said clarifier may be basedon sorbitol, modified sorbitol chemistry, or other nucleating agentsuitable for the promotion of the crystallization of PP, maybe added toensure that the optical density of the resulting film is less than 0.7%,if a clear film is required. However other optical density can beselected within the field of the invention, and for many applicationswhere only good contact clarity or else the film will be colored and/orpigmented or printed it may or may not be necessary to include aclarifying agent or use a preclarified grade of polypropylene.

According to a second preferred embodiment, the invention relates to amethod of forming, sealing and filling a pouch with a liquid, powder,granules and/or other flowables at high speed, said method comprisingthe steps of:

-   -   i) providing, in roll form, a multi-layer film as defined        hereinbefore,    -   ii) drawing said film, by drawing means, over a pouch former to        form a plastic film tube having an overlapped vertical film        edge,    -   iii) sealing said overlapped vertical edge with a vertical        sealer to form a vertical seal,    -   iv) effecting a horizontal seal across said plastic film tube        with a horizontal sealing jaw and at a predetermined location        below said vertical sealer, and simultaneously severing said        tube to form a top horizontal seal for a filled pouch and a        bottom horizontal seal for a pouch being filled, said horizontal        and vertical seals, and    -   v) continuously feeding a consumable liquid, powder, granules        and/or other flowables within said plastic film tube below said        vertical sealing jaw and above said transverse sealing jaw.

Advantageously, said method is processed on a high speed vertical form,fill and seal system as shown in FIG. 1.

Blown film coextrusion is a highly versatile technology covering a widerange of applications including complex structures based on 2 or more(preferably 2 to 9) layers—but not limited to 9 at the upper limit tothe number of layers—of the same or different materials.

As shown in FIG. 2, melted polymer is extruded through a circular dieand the tube is filled with air to blow it. Many parameters areadjustable to achieve the right properties. Technique of blown filmco-extrusion are well known to skilled workmen and do not need to bedescribed in detailed. This process may be summarized as follows: Amultilayer blown film processing extrusion line such that two skinlayers and a core with at least one layer is prepared. The skin layerswill be prepared with a blend of linear low density polyethylenes with adensity such that the seal initiation temperature is sufficiently low toachieve rapid sealing during vertical form fill and seal operation. Thetypical LLDPE may preferably have densities from 0.915 g/cc to 0.89g/cc. The core maybe a single layer of a random copolymer polypropyleneblended with a polypropylene-polyethylene compatibiliser. A suitablecompatibiliser being ethylene methacrylate copolymer (EMAC) with amethacrylate content of 20%, or one or another (or combination there of)from the list of compatibilisers and/or tie-layer resins providedherein. The core may also be a single layer of polypropylene (PP)blended with linear low density polyethylene (LLDPE) and acompatibiliser such as ethylene methacrylate copolymer (EMAC) or one oranother polymer selected from the list of compatibilisers providedherein. Preferably the film will be prepared with a blow up ratio(B.U.R) of at least 2. A multilayer core may also be produced, of layersof polypropylene or polypropylene-polethylene blends with a suitablecompatibiliser or tie-layer polymer such as EMAC or other materialdetailed in the list of tie-layers or compatibilizers above.

Optionally, the outer layer, the core and/or the inner layer may furthercomprise one or several additives useful to make easier the processingof a film in a vertical form, fill and seal system, such as for examplepolymer processing aids concentrate and/or slip/antiblock concentrates.Any of such additives well known to skilled workman can be used.Advantageously, the following additives are particularly preferred:

Slip Agent:

200 to 2000 ppm of a “slip” agent well known to skilled workman. Aprefered slip agent is erucamide or other fatty acide amide such asoleamide. The slip agent lowers the coefficient friction of the film andallows it to slide readily over various surfaces;

Anti-Blocking Agent:

1000 to 5000 ppm of any film anti-blocking agent well known to skilledworkman maybe added to the film layers. Preferably from 1000 to 5000 ppmof an anti-blocking material such as diatomaceous earth, syntheticsilica or talc will be added to the inner and outer layers of the film.The anti-blocking material is particularly useful in reducing thecoefficient of friction between the film and the metallic surfaces overwhich the film is drawn during the VFFS process.

Processing Aid:

50 to 1000 ppm of any processing aid well known to skilled workman,preferably and not limitatively a 150 to 500 of a fluoro-elastomer basedpolymer processing aid maybe added to outer and inner skin layers of thefilm.

In the following particularly preferred example, the formulation of eachlayer is as described hereinafter.

Preferably, said multi-layer may comprise:

-   -   an inner layer made from the mixture of:        -   79.10% of ATTANE 4201 (ultra low density ethylene/octane            copolymer; density: 0.912 g/cm³;);        -   18.50% of DOW Polyethylene 133A (low density polyethylene;            density: 0.923 g/cm³);        -   1.85% of a concentrate of 50,000 ppm erucamide as slip agent            and 100000 ppm of diatomaceous earth or other suitable film            anti-blocking agent; density: 0.980 g/cm3);        -   0.55% of a 3% fluoro-elastomer based polymer processing aid            (PPA) concentrate to reduce the tendency of the            metallocene-LLDPE (m-LLDPE) layer or ultra-low LLDPE            (u-LLDPE) to have melt fracture or sharkskin;        -   a core layer made from the mixture of:        -   from 62 to 68.85% or more of polypropylene (PP) such as for            example one or combination of DOW PP D114.01 (ρ=0.903 g/cc,            melt flow rate 0.42 g/10 min (ASTM 1238) or Sonoco PP TI            4007G (ρ=0.9 g/cc, melt flow rate 0.7 g/10 min (ASTM 1238)            or Total Petrochemicals PP 4170 (ρ=0.905 g/cc, melt flow            rate 0.75 g/10 min (ASTM 1238));        -   27.6% to 20.85% of NOVA FP026-F (linear low density            polyethylene; density: 0.926 g/cm3) or similar LLDPE;        -   8.00% of EMAC SP 2207 (20% methacrylate content, ρ=0.941            g/cc, melt index 6.00 g/10 min (ASTM D1238, 2.16 kg, 190°            C.) as compatibilizer; density: 0.941 g/cm3);        -   1.15% of a 5% erucamide or other suitable slip concentrate.            The required amount of slip is such that the coefficient of            friction of the film after equilibration of the slip in the            film is such that the film moves smoothly through the VFFS            filler;        -   1.150% of a 10% polypropylene clarifier/nucleating-agent            concentrate. A suitable nucleating agent is Bis (p-methyl            benzylidene sorbitol). The clarifier may not be necessary            for those applications where the goal is merely to have good            contact clarity.        -   an outer layer made from the mixture of:        -   79.10% of EXXON MOBIL EXCEED 1012CA (mVLDPE resin; density:            0.912 g/cm³);        -   18.50% of DOW Polyethylene 133A (low density polyethylene;            density: 0.923 g/cm³);        -   1.85% of a concentrate of “50,000 ppm erucamide as slip            agent and 100000 ppm of diatomaceous earth or other suitable            film anti-blocking agent        -   0.55% of a 3% fluoro-elastomer based polymer processing aid            (PPA) concentrate to reduce the tendency of the            metallocene-LLDPE (m-LLDPE) layer or ultra-low LLDPE            (u-LLDPE) to have melt fracture or sharkskin.

More particularly, with reference to FIG. 1, there is shown generally at10 basic component parts of a high-speed pouch forming, filling andsealing machine constructed in accordance with the present invention.These basic component parts are only schematically illustrated and arewell known in the art. The improvement in the machine resides primarilyin the vertical sealer operating characteristics and the horizontalsealing jaws characteristics, as will be described later. The sealersare controlled to operate with a new multi-layer film whereby toincrease the throughput of the machine and provide filled pouches havingimproved strength and wherein the seals are greatly improved over thoseof the prior art, thereby resulting in a machine which can output morefilled pouches, achieve a significant waste reduction and less downtimeas compared with prior art machines using a 76 microns (3 mil)mono-layer polyethylene film. As herein shown the high-speed pouchforming, sealing and filling machine comprises a film roll 11 providedwith a multi-layer film 12 which is guided through guide rolls andtensor rolls 13 to a top end of a pouch former 14 where the plastic filmis guided and folded to form a plastic film tube 15 having an overlapvertical film edge 16. A filler tube 17 extends within the pouch former14 and the tube 15 and has a liquid discharge end 17′ positioned at afilling location 18.

A vertical sealer 19 has a sealing head 20 provided with a heatingelement 21 and a backing member 22 is disposed vertically aligned behindthe overlap vertical film edge 16. A vertical seal is formed by fusingthe overlapped edge 16 along the plastic tube 15 above the fillinglocation 18. A horizontal sealing jaw assembly 23 is provided spaced ata predetermined distance below the filling location 18 whereby to form ahorizontal seal across the film tube 18 and at the same time sever thetube to form a sealed pouch 24 filled with a consumable liquid 25therein. The pouch is then released on a discharge conveyor 26.

The horizontal sealing jaw assembly 23 is comprised of a sealing head 27provided with an electrical impulse sealing wire element 28 to sever thefilm tube as well as to form a top horizontal seal 29 for the pouch 24and a bottom horizontal seal 30 for the next pouch being formed hereinillustrated by reference numeral 24′. The horizontal sealing jawassembly 23 also has a backing member 31 which is provided as a rubberor Teflon® pad 32 to serve as a backing for the electrical impulsesealing wire element 27. From time-to-time it is necessary to change thepad and the wire element as they wear down. By operating at lowertemperature, 1020 C.-15° C. lower than the prior art discussed above,these elements have a longer life cycle and there is less machinestoppages. The jaw assembly 23 may move in and out in unison to form theseal or the backing member 31 may be stationary and positioned close tothe film with only the sealing head 26 moving in and out. Other suitablesealing assemblies are conceivable provided they can achieve the sameresults. The film sheet 12 is drawn in continuous motion by a pair ofdraw rolls 33 in a manner well known to the art. So far we havedescribed the basic component parts of a well known pouch forming,sealing and filling machine such as the Thimonnier M3200®, ThimonnierM5200® or a Prepak IS-7®.

The present invention resides in the provision of a novel multi-layerfilm structure in combination with the machine to enhance theperformance of the machine. This enhancement is achieved by controllingthe temperature of the sealing assemblies 19 and 23 wherein they operateat temperatures that are lower than prior art machines. The draw rolls33 are also operated at higher speeds whereby to increase the throughputof the machine while producing horizontal seals which are much superiorthan the above-mentioned prior art machines and resulting in aproduction having less post consumer waste and permitting the machine tooperate with less downtime previously caused by malfunction or plasticfilm roll change.

Typical Comparative Data

Table I with reference to the enclosed FIGS. 3 to 7, shows a formulationwhich show respectively tensile, secant modulus (stiffness) and breakstrength data, highlights the improvement in physical properties thatare possible when high levels of PP are used in conjunction with thecompatibilizer EMAC. The films coded RS3 contain EMAC. The numbers inthe code represent the film thickness i.e. 2.0 or 2.25 mil. The EMACchanges the crystal structure of the PP-LLDPE blend used in the core tosuch an extent that this layer has:

-   -   i) A strength and stiffness like PP;    -   ii) The ability to be blown into film more easily than the high        melt temperature component (PP);    -   iii) Sufficient compatibility with the other layers so no        delamination occurs.

Delamination of film layers will compromise the film strength andperformance. TABLE 1 2.25 mil thick milk pouch film formulation (RS3)for increased/improved physical properties and good seal integrity inhigh speed VFFS machines Exterior of Bags/Interior of BagInterior/Exterior Bubble Middle layer of Bubble Material (%) Material(%) Material (%) ULLDPE 75.60 LLDPE 25.85 m-LLDPE/v- 75.60 LLDPE LDPE22.50 EMAC 4.00 LDPE 22.50 Polymer 0.5 PP 68.85 PPA 0.5 processingD114.00 aid Concentrate Slip/ 1.9 Slip 1.30 Slip/ 1.9 antiblockanti-block (5%/10%) (5%/10%) concentrate concentrateN.B. for the data shown in the accompanying figures the outer and innerlayer formulations were held constant while the proportion of EMAC andthe relative ratio of PP to LLDPE in the core-layer were varied. Theratio outer layer:core layer:inner layer being 25:50:25.

The film coded as D-2.75 is a commercially available 2.75 mil mono-layerpolyethylene film that is often used in VFFS systems for the packagingof milk. The films coded RS2 clear or RS2 blue, are three layer filmswith a blend of LDPE, LLDPE and PP in the core but no EMAC. The lack ofEMAC and/or compatibilizer, the presence of LDPE and the relatively lowamounts of PP limits the strength and efficacy of these films relativeto the “RS3” films.

Hereinafter are alternative embodiments of the above preferredembodiment of the invention showing variations in the content of eachlayers.

A first set of alternative preferred embodiments relates to amulti-layer film having a relatively lower melt index polypropylenecopolymer and LLDPE in the core layer.

More particularly, this first set of alternative preferred embodimentsrelates to a multi-layer film having the following characteristics:

-   -   The film is 2.25 mil thick with three layers (inner layer to        outer layer) in the ratio of 25:50:25.    -   The type of polypropylene (copolymer) has a melt flow index        (MFI) of 0.4 g/10 min (ASTM 1238, 230° C., 2.16 kg) and a        flexural modulus 218716 psi (for example DOW® 114.01).    -   The LLDPE has a melt index of approximately 0.8 g/10 min (ASTM        1238; 190° C, 2.16 kg) and a density of 0.926 g/cc, (for example        NOVA® FP 026. )    -   The compatibilizer is an ethylene methyl acrylate copolymer (20%        methyl acrylate content) such as Eastman SP2207®.    -   Inner layer is 75.60% of a uLLDPE (density 0.912 g/cc), 22% of        fractional melt LDPE (eg density=0.923, MI=0.22) together with        2.4% slip anti-block and other processing additives.    -   Outer layer is 75.60% of a vLLDPE (denity 0.912 g/cc), 22% of a        fractional melt LDPE together with 2.4% of slip and anti-block        and other polymer processing additives    -   The core layer also contains 1.3% of a 5% slip concentrate as a        slip agent.

The following table 2 illustrates data for three layer—inner layer/corelayer/outer layer—(25:50:25)—co-extruded film made with relatively lowermelt index polypropylene copolymer and LLDPE in the core. TABLE 2Physical Properties (MD = machine direction; CD = cross direction)Composition of the core layer Tensile Tensile 1% Tensile Tensile 1% PP-Stress at Break Secant Stress at Break Secant Copolymer Yield StrengthModulus Yield Strength Modulus Compatibilizer (MFI = 0.4) LLDPE (MD)(MD) (MD) (CD) (CD) (CD) 4.0 20 74.70 2030 5570 102000 1330 5000 1090004.0 90 4.70 3300 6120 133000 3200 6200 130400 2.5 20 76.20 2500 436071600 1970 4600 5500 2.5 90 6.20 3200 7400 148300 2900 5600 167500N.B. Films with a lower melt index polypropylene in the core can berelatively stiffer as determined by 1% secant modulus because of thegreater flexural modulus of the polypropylene. All composition data arein weight % and physical properties data are in psi. Complement of thecomposition to 100 weight % consists of additives such as slip agent oranti-block agent.

A second set of alternative preferred embodiments relates to amulti-layer film having a relatively relatively higher indexpolypropylene copolymer and LLDPE in the core layer.

More particularly, this second set of alternative preferred embodimentsrelates to multi-layer films having the following characteristics:

-   -   The film is 2.25 mil thick with three layers (inner layer to        outer layer) in the ratio of 25:50:25.    -   The type of polypropylene (copolymer) has a melt flow index of        approximately 0.7 g/10 min (ASTM 1238, 230° C., 2.16 kg) and a        flexural modulus of 175000 psi (for example Sunoco TI4007G)®    -   The LLDPE has a melt index (MI) of 0.8 g/10 min (ASTM 1234, 190°        C., 2.16 kg ) and a density of 0.926 g/cc, (for example NOVA FP        026)®.    -   The compatibilizer is an ethylene methyl acrylate copolymer (20%        methyl acrylate content) such as Eastman SP2207®.    -   Inner layer 1 is 79.10% of a uLLDPE (density 0.912 g/cc), 18% of        fractional melt LDPE (eg 0.923 g/cc, MI=0.22) together with 2.9%        slip and anti-block and other processing additives.    -   Outer layer 2 is 80.60% of a vLLDPE (denity 0.912 g/cc), 18% of        a fractional melt LDPE (eg 0.923 density & MI=0.22) together        with 1.4% of slip and anti-block agent    -   The core layer also contains 1.3 of a 5% slip concentrate.

The following table 3 illustrates data for three layer—inner layer/corelayer/outer layer—(25:50:25)—co-extruded film made with relativelyhigher index polypropylene copolymer and LLDPE in the core. TABLE 3Physical Properties (MD = machine direction; CD = cross direction)Composition of film core layer Tensile Tensile 1% Tensile Tnesile 1% PP-Stress at Break Secant Stress at Break Secant Copolymer Yield StrengthModulus Yield Strength Modulus Compatibilizer (MI = 0.7) LLDPE (MD) (MD)(MD) (CD) (CD) (CD) 8 15.00 75.20 1725 4796 38150 3637 2073 40800 890.20 0 2826 6281 76729 4802 2348 75188N.B. Films with a higher melt index polypropylene in the core can berelatively more flexible as determined by 1% secant modulus because ofthe lower flexural modulus of the polypropylene. The choice ofpolypropylene may be used to partially determine the final filmstiffness. All composition data are in weight % and physical propertiesdata are in psi. Complement of the composition to 100 weight % consistsof additives such as slip agent or anti-block agent.

A third set of alternative preferred embodiments relates to amulti-layer film having a relatively relatively higher indexpolypropylene copolymer and LLDPE in the middle layer.

More particularly, this third set of alternative preferred embodimentsrelates to multi-layer films having the following characteristics:

-   -   The film is approximately 2.25 mil thick with three layers        (inside layer to outside layer) in the ratio of 20:60:20.    -   The type of polypropylene (copo) has a melt flow index of        approximately 0.7 g/10 min (ASTM 1238, 230° C., 2.16 kg) and a        flexural modulus of 175000 psi (for example Sunoco T14007G)®.    -   The LLDPE has a melt index of approximately 0.8 g/10 min (ASTM        1234, 190° C., 2.16 kg ) and a density of 0.926 g/cc, (for        example NOVA FP 026)®.    -   The compatibilizer is an ethylene methyl acrylate copolymer (20%        methyl acrylate content) such as Eastman SP2207®.    -   Inner layer 1 is 79.10% of a uLLDPE (density 0.912 g/cc), 18% of        fractional melt LDPE (eg 0.923 g/cc, MI=0.22) together with 2.9%        slip anti-block and other processing additives.    -   Outer layer 2 is 80.60% of a vLLDPE (denity 0.912 g/cc), 18% of        a fractional melt LDPE (eg 0.923 density & MI=0.22) together        with 1.4% of slip and anti-block additives.

The following table 4 illustrates data for three layer—inner layer/corelayer/outer layer—(20:60:20)—co-extruded film made with lower melt indexpolypropylene copolymer and LLDPE in the core layer. TABLE 4 PhysicalProperties (MD = machine direction; CD = cross direction) Composition offilm core layer Tensile Tensile 1% Tensile Tensile 1% PP- Stress atBreak Secant Stress at Break Secant Copo Yield Strength Modulus YieldStrength Modulus Compatibilizer (MI = 0.4) LLDPE (MD) (MD) (MD) (CD)(CD) (CD) 8% 15.0 75.20 1741 4898 35922 1697 3698 41410 8% 90.2 0.0 27176368 75285 2025 4433 75285N.B. Films with a higher melt index polypropylene in the core can berelatively more flexible as determined by 1% secant modulus because ofthe lower flexural modulus of the polypropylene. The choice ofpolypropylene together with the ratio of the layer# thicknesses and the percentage of the compatibilizer in the core maybeused to partially determine the final film stiffness. All compositiondata are in weight % and physical properties data are in psi. Complementof the composition to 100 weight % consists of additives such as slipagent or anti-block agent.

Of course, the above description of the embodiments of the invention isnot limitative and also comprises all possible variations andembodiments that may seems obvious to a man skilled in the art.

1. A multi-layer film for vertical form, fill and seal systems forliquid, powder, granules and/or other flowables packaging, saidmulti-layer comprising: an inner layer made of polyethylene, a blend ofone or several polyethylenes and/or one or several ethylene copolymers;a core, comprising one or more than one layer, made from a blend of:polypropylene; linear low density polyethylene; a polymer compatibilizeror tie-layer resin; and/or optionally low density polyethylene; saidcore being applied against the inner layer; and an outer layer (same ordifferent from the inner layer or the core layer) is made of apolyethylene or a blend of one or several polyethylenes with or withoutone or several ethylene copolymers, said outer layer being appliedagainst the core and opposite the inner layer; said multi-layer filmhaving an overall thickness of lower or equal to 2.5 mil.
 2. Amulti-layer film according to claim 1, wherein said film has an overallthickness of 1.75 to 2.5 mil.
 3. A multi-layer film according to claim1, wherein the relative thickness of the inner layer:core layer:outerlayer vary from 10:80:10 to 30:40:30.
 4. A multi-layer film according toclaim 2, wherein the relative thickness of the inner layer:corelayer:outer layer is 25:50:25.
 5. A multi-layer film according to claim3, wherein said film further has at least one of the properties listedhereinafter: a stiffness (as measured by 1% secant modulus in filmmachine direction) varying from 3500 psi to 150000 psi; and a tensilestrength at yield of from 1700 psi to 3300 psi (measured in film machinedirection); and. a tensile strength at break of from 4300 psi to 7400psi (measured in film machine direction).
 6. A multi-layer filmaccording to claim 5, wherein said film at least has a stiffness (asmeasured by 1% secant modulus) varying from 3500 psi to 150000 psi.
 7. Amulti-layer film according to claim 1, wherein the blend defining thecore layer comprises in weight percent: 10% to 90% of polypropylene or amixture of polypropylenes; 80% to 0% (lower limit not comprised) of alinear low density polyethylene or a mixture of linear low densitypolyethylenes and low density polyethylene; and 2% to 10% of at leastone polymer compatibilizer.
 8. A multi-layer film according to claim 7,wherein the polymer compatibilizer is selected from the group consistingof ethylene methacrylate, ethylene methacrylate copolymer, ethylenebutyl acrylate, ethylene vinyl acetate, ethylene propylene diaminerubber, ethylene propylene copolymer; ethylene styrene copolymer, and/orethylene thermoplastic elastomers.
 9. A multi-layer film according toclaim 7, wherein the polypropylene is a random copolymer polypropyleneor blend of homo-polymer polypropylene and copolymer polypropylene. 10.A multi-layer film according to claim 9, wherein the polypropylene has agrade of polypropylene or blend of polypropylene allowing to prepare amulti-layer film having a high impact strength, the izod impact strengthof the polypropylene being greater than 9 ft.lb_(f) per inch of notch asper American Society for Testing and Materials (ASTM) D256.
 11. Amulti-layer film according to claim 8, wherein the ethylene methacrylatecopolymer has from 10 to 25% of methacrylate content.
 12. A multi-layerfilm according to claim 8, wherein the linear low density polyethylenefor the core layer has a melt index (ASTM D1234, 2.16 kg, 190° C.) from0.4 to 2.00 g per 10 minutes and a density of approximately 0.926 g/cc.13. A multi-layer film for vertical form, fill and seal systems forliquid, powder, granules and/or other flowables packaging, saidmulti-layer comprising: an inner layer made of an octene-LLDPE (or otherLLDPE) blended with low density polyethylene; a single and/ormulti-layer core made from a blend in weight percent of: 10% to 90% ofpolypropylene; 80% to 0% (lower limit not comprised) of a linear lowdensity polyethylene or low density polyethylene and a polymercompatibilizer of from 2.5 to 12%, said core being applied against theinner layer; an outer skin layer made of an LLDPE, blended with lowdensity polyethylene. said multi-layer film having an overall thicknessvarying between 1.75 to 2.5 mil for the packaging of 0.8 to 1.7 kg ofliquid, powder, granules and/or other flowables or flowables a stiffnessvarying from 3500 psi to 150000 psi (measured in film machine direction)as measured by the 1% secant modulus ; and a tensile strength at yieldof from 1700 psi to 3300 psi (machine direction) and a strength at breakof from 4300 to 7400 psi (machine direction).
 14. A method of forming,sealing and filling a pouch with a liquid, powder, granules and/or otherflowables at high speed, said method comprising the steps of: i)providing, in roll form, a multi-layer film as defined in claim 1, ii)drawing said film, by drawing means, over a pouch former to form aplastic film tube having an overlapped vertical film edge, iii) sealingsaid overlapped vertical edge with a vertical sealer to form a verticalseal, iv) effecting a horizontal seal across said plastic film tube witha horizontal sealing jaw and at a predetermined location below saidvertical sealer, and simultaneously severing said tube to form a tophorizontal seal for a filled pouch and a bottom horizontal seal for apouch being filled, said horizontal and vertical seals, and v)continuously feeding a consumable liquid, powder, granules and/or otherflowables within said plastic film tube below said vertical sealing jawand above said transverse sealing jaw.
 15. A method of forming, sealingand filling a pouch with a liquid, powder, granules and/or otherflowables at high speed, said method comprising the steps of: i)providing, in roll form, a multi-layer film as defined in claim 11, ii)drawing said film, by drawing means, over a pouch former to form aplastic film tube having an overlapped vertical film edge, iii) sealingsaid overlapped vertical edge with a vertical sealer to form a verticalseal, iv) effecting a horizontal seal across said plastic film tube witha horizontal sealing jaw and at a predetermined location below saidvertical sealer, and simultaneously severing said tube to form a tophorizontal seal for a filled pouch and a bottom horizontal seal for apouch being filled, said horizontal and vertical seals, and v)continuously feeding a consumable liquid—or powder, granules and/orother flowables—within said plastic film tube below said verticalsealing jaw and above said transverse sealing jaw, the resulting pouchhaving walls provided with a thickness varying from 1.75 to 2.5 mil andat least one of the properties listed hereinafter: a stiffness varying3500 psi to 150000 psi (as determined by 1% secant modulus in the film'smachine direction); and a tensile strength at yield of from 1700 psi to3300 psi (machine direction); and tensile strength at break from 4300 to7400 psi (machine direction).
 16. A method of forming, sealing andfilling a pouch with a liquid, powder, granules and/or other flowablesat high speed, said method comprising the steps of: i) providing, inroll form, a multi-layer film as defined in claim 13, ii) drawing saidfilm, by drawing means, over a pouch former to form a plastic film tubehaving an overlapped vertical film edge, iii) sealing said overlappedvertical edge with a vertical sealer to form a vertical seal, iv)effecting a horizontal seal across said plastic film tube with ahorizontal sealing jaw and at a predetermined location below saidvertical sealer, and simultaneously severing said tube to form a tophorizontal seal for a filled pouch and a bottom horizontal seal for apouch being filled, said horizontal and vertical seals, and v)continuously feeding a consumable liquid within said plastic film tubebelow said vertical sealing jaw and above said transverse sealing jaw,the resulting pouch having walls provided with a thickness varying from1.75 to 2.5 mil, a stiffness varying 3500 psi to 150000 psi (asdetermined by 1% secant modulus), a tensile strength at yield of from1700 psi to 3300 psi (machine direction) and a tensile strength at breakfrom 4300 to 7400 psi (machine direction).
 17. A pouch obtained from amulti-layer film as defined in claim 1 on a forming, sealing and fillingsystem.
 18. A pouch obtained from a multi-layer film as defined in claim13 on a forming, sealing and filling system.
 19. Use of a multi-layersfilm as defined in claim 1 for preparing a pouch by processing on a highspeed vertical form, film and seal systems.
 20. Use of a multi-layersfilm as defined in claim 13 for preparing a pouch by processing on ahigh speed vertical form, film and seal systems.